The present invention relates to a method of diagnosing magnification, linearity and stability of a scanning electron microscope.
In scanning electron microscope it is very important to determine each major parameter, such as magnification, linearity, and stability. There are different methods of diagnosing a magnification with the use of reference material and interpretation of the results in a semi-manual form. No methods have been known for diagnosing of linearity and stability. It is therefore believed to be advisable to provide new methods for diagnosing of the above mentioned parameters.
Accordingly, it is an object of present invention to provide a new method of diagnosing magnification, linearity, and stability of a scanning electron microscope.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a method of diagnosing magnification, linearity, and stability of scanning electron microscope which includes loading a reference material into a microscope; setting a permissible limit of a value of the parameters; inputting a pitch of the reference material; inputting a magnification of the microscope; acquiring a set of digital images on the reference material; analyzing the digital image line after line with determination of a pitch of features of the image in each line, in mutually orthogonal directions; checking if all lines of the digital image has been analyzed; determining a mean value of the pitch of the features in each orthogonal direction; comparing the obtained value of the pitch of the image with a known value of the pitch of the reference material to determine a ratio indicative of a modification; and determining a precision of the measurements of the pitch by statistical analysis of the pitch measurements.
In accordance with another feature of present invention said obtaining includes obtaining a set of digital images, and performing the subsequent steps for each of the images.
In accordance with another feature of present invention the method includes the step of selecting to diagnose a respective one of the magnification, linearity and stability after loading of the reference material.
In accordance with another feature of present invention, when the parameter is a magnification, said analyzing the pitch between the features in each line includes using the pitches of all determined lines.
In accordance with another feature of present invention, when wherein the parameter is a linearity, said analyzing includes determining the pitches separately for various areas of the image, and thereafter determining a magnification for each of the areas.
In accordance with another feature of present invention, when the parameter is a stability, said analyzing includes comparing the determined linearities in time.